The present invention pertains to pharmaceutical injection devices, and, in particular, to a priming mechanism for an automatic injection device.
Currently, biologic drugs account for more than half of all therapeutic drug candidates in pharmaceutical development pipelines. These biologic drugs need to be delivered through the parenteral route. As the parenteral therapeutic drugs become more and more popular, portable automatic medication delivery devices for self-administration are expected to be widely used together with the parenteral therapeutic drugs (also referred as combination products). One type of such device is an automatic injector device. This type of device, when triggered by a user, automatically inserts into the user a needle of a pre-filled syringe that prior to triggering was disposed within the device housing, and then automatically injects a dose of medication through that inserted needle. One difficulty with designing an automatic injector is ensuring that air bubble inside the pre-filled syringe is removed before injection (priming). This is especially true for automatic injector devices that deliver variable dose. Moreover, priming is also an essential step for using dual chamber reconstitution syringe as medication container in an automatic injector device.
International Publication Number WO 2016/036600 explains in additional details about automatic injector devices that deliver variable dose. For the variable dosing automatic injectors, it is important to remove the air bubble before injection in order to deliver correct dose. Therefore, it would be desirable to provide a priming mechanism for those automatic injection apparatus.
Besides, the priming mechanism in this invention can be utilized for automatic injector devices that carry dual chamber reconstitution syringes. Example of dual chamber reconstitution syringes can be Vetter Lyo-Ject® dual-chamber syringe or dual chamber reconstitution syringe used for leuprolide acetate injection (Lupron Depot®). To utilize automatic injector devices with reconstitution syringe, it is important to mix liquid form and dry form contents immediately prior to application.
In summary, what is needed is a new priming mechanism for utilizing automatic injector device when delivering variable dose or mixing different contents before injection.